Apparatus for indicating teletypewriter speeds



June 10, 1947. w. B. MARTIN 2,421,954

APPARATUS FOR INDICATING TELETYPEWRITER SPEED vFiled Oct. 20. 1944 2 Shee'cs-Shee l l H mi i b5 'i i i @E 2 Si l 2 @v -WH @www LH i LLM- Hl 8 a Imi ATTORNEY 111116101947. w. N1/4mm 2,421,954

APPARATUS FOR INDIGATING TELETYPEWRITER SPEED Filed oct. 2o, 1944 2 sheets-sheet 2 ATTORNEY Patented June 10, 1947 APPARATUS FOR INDICATING TELETXPE- `WRITER SIEEDSy 'Wade E; ltartin, Ramsey, N. QJ., .assigner to i American Telephone and Telegraph Company, a'corporation of New York Application October 20, 1944, Serial No. 559;"622

. l This invention relates to teletypewriter Vapparatus and more particularly to arrangements for indicating the speed at whicha te'letypevvriter is rransmitangsignais.

When an automatic teletypewriter transmitter is ,transmitting teletypewriter signals `of the start-stop ,type over .a wired circuito-r radio path to a teletypewriter receiver, thesignals will ordinarily be reproduced with good intelligibility if the transmitter vand receiver .are operatingat the same speed. If the transmitter speed should change during transmission, 'the teletypevvriter signals reproduced Will become distorted. In fact, a small change in the speed of the 'teletypewriter transmitter may ofttirnes 'be "suiiicient to render the signals reproduced unintelligible. Such conditions have been `found rto arise particularly Where the automatic teletypewriter -9 Claims. (Cl. 178--69)A transmitter was supplied with power `from 'an unregulated source Vor where `its motor was controlled by a governor.

`It -is `therefore one Of the objects -o'f this invention to provide simple-apparatus forfmeasuring -or observing the speed `of `operation `of an automatic teletypewriter transmitter.

rlUhis object may be accomplished by employing apparatus which converts the transmitted signals into letters Ysignalsl and `combines the latter signals with other letters signals obtained from a local -teletypewiliiter operating 'at "its `optimum speed. If the rletters signals are received ff-rom both sources at thesame speed, that is, if these :two groups `rof yfletters Vsignals are received synchronously, lthen the third signal obtained from their combination Ywill continuously repeat itself. 'This fthird signal will also be letters if `:the component signals are in'phase with eachother. That is, lif vthe two 'groups di letters signals are received synchronously and in phase, `the resultant signal Will be `fthe `same letters signal. If the two groups of"letters signals are received synchronously but out-of phase .with `each other, `any one of live other signals, namely, "V, X, gures, Qor K, `will betpro'duced by their combination, the parti'cularsignal obtained :from the combination depending ion the phase difference -of the Vtvvo groups of iletters signals. 'Onthe other hand, if the two groups of letters vsignals are received at different speeds, repeated signals V, 1X, figures, Q, K land lettersv Will appear in a cycle and the cycle will be reproduced in succession. The number o'f `times -each signal vis reproduced `in succession While passing `through its .cycle will be :a measure of fthe -fdiierence in speed between `the .local teletypewriter transmitter rand .the automatic teletypewriter Atransmitter which is being=obser'.ved.

.This invention will be 4better understood from the more` detailed description hereinafter Qiollowing When Tread in connection with the ace companyng .drawing in `Which JFigure .1 illustrates one embodiment of the invention given merely forillustrative purposes, Fig.` 2 showsia counting circuit suitable 'for .-use with the ,arrangement of Fig. 1, .and Fig. Bishows .curves to explain .certain of the phenomena of the apparatus of :the invention. i

Referring to Fig. 1 o'f .the drawing, .thereis shown the transmitter-.distributor "ID of an automatically operated teletypewriter, which may be of 'any well-known type capable Aof ,producing signals .of` .the .start-stop type. The l-ve-fpulse signals ,produced by the Vtransmitter-distributor are modulated `on a radio Wave at the radio transmitter RT and are radiated through `space by `the transmitting antenna TA. These .radio signals are `received by the receiving vantenna RA, Vthen demodulated at htheradio receiver RR, the demodulated nsignals, 4being transmitted through 'the ,telegraph repeater 'TR `in a Wellknownmannerto the teletypewriter receiver 'TYR where Athe signals maybe reproduced in typed form. If the automatic transmitter-distributor TD is operating at the samespeed .as the teletypewriterreceiver TYR, thesignals Will ordinarily be reproduced intelligbly. However, if the speed ofthe transmitter-distributor TD should increase ordecrease so as to `be `out of step with the .teletypewriter receiver TYR, the reproduced signals may become unintelligible. Apparatus "for observing .the 'speed deviation o`f the distant `transmitter-tlistributor will now 'be described. r i.

A monitoring 'teletypewriter MTY, y.which may be; of 'theNo `1.4 or No. `15 type, for example, is connected to the .output :side of the 1telegraph repeater 'TR and in series with the teletypewriter receiver TYR. 'The monitoring .teletypewriter is equipped with universal or commonV con tacts "K1-K2 which will be opened and closed once 'for each signal received from the transmitterdistributor TD or `for each 'operation performed bythe transmitter-distributor TD. In otherfwords, the universal contactsKi-Kz will be opened once and closed once for each `group of pulses corresponding to a signal or character transmitted by the transmitter-distributor TD and :received via the telegraph repeater 'TR by the teletypewnter :rheuma/@rsa1 contact structure K1-Kz is of well-known type and is shown and described, for example, in the application of W. M. Bacon et al., Serial No. 248,426, iled December 30, 1938. The contact K1 is connected to a negative battery B1 which is grounded, and contact K2 is connected toa positive battery B2 which is also grounded. The contact K1 is also connected to a condenser` Q and the upper winding W1 of a relay R. The lower winding W2 of relay R is connected to a battery B3 which supplies current continuously thereto to bias the armature of the relay to its contact M. The armature and contact M of relay R are connected in a series circuit which includes battery B4, the armature and contact M of relay R, the receiving winding RW and transmitting contacts TC of a teletypewriter TTY and battery B5. The teletypewriter TTY may be of the No. 14 type, for example, arranged for repeat keyboard operation, and its motor (not shown) should rotate at the optimum speed for the system. The motor may be of the synchronous type if its driving power frequency is adequately controlled so that it may maintain a constant speed of operation. When the letters key of this teletypewriter TTY is pressed and locked down, the letters character or signal will be reproduced 368 times per minute, for example, on a 60 speed circuit. Y

When the monitoring teletypewriter MTY is receiving no signals from the transmitter-distributor TD, the universal contactsK1-K2 will be held closed and there will be no charge on condenser Q. The current in winding W1 of relay R will then be a nullity and hence the armature of relay R, acting under the iniiuence of the biasing current in winding W2, will be held against its contact M. The armature of relay R will be held against its contact M whether signais are being transmitted by the transmitting contacts TC of teletypewriter TTY, or when no signals are being so transmitted. It is preferable to keep teletypewriter TTY unoperated until signals are received by its receiving winding y RW and to operate the teletypewriter TTY by locking its letters key only when signals are being received from relay R, but the invention can be carried out even if teletypewriter 'ITY is producing letters signals continuously, even when no signals are being received by the receiving winding RW from the relay R.

Y When the monitoring teletypewriter is receiving a signal from the automatic transmitter-distributor TD via the telegraph repeater TR, the contacts Ki-Kz will rst be opened and then closed. As soon as contacts Kr-Kz are opened, the battery B1 will be connected in series with condenser Q and the winding of relay R. An increasing charge will be applied to condenser Q, rendering its left-hand terminal negative with respect to its right-hand terminal. The charging current traversing the winding W1 will be suiicient to overcome the biasing effect of winding W2 and hence the armature of relay R will be moved to its contact S. A spacing pulse will then be received by the receiving winding RW of teletypewriter TTY and this pulse will start the teletypewriter TTY in operation. This pulse will cause the teletypewriter TTY to register a letters signal or character. As soon as the charging current through winding W1 has been sufficiently reduced in magnitude, the armature of relay R will be returned to its contact M. Moreover, the contacts K1-K2 will become closed before the next signal is received by the monitor- 4 ing teletypewriter MTY. The constants ol the series circuit of condenser Q have been chosen so as to have the armature of relay R open its contact M for about 22 milliseconds.

W'hen another teletypewriter signal is received by teletypewriter MTY, the contacts B21-K2 will again be opened once and then closed and a like signal will be registered by teletypewriter TTY. This cycle will be repeated as often as signals are received by teletypewriter MTY. The starting pulse transmitted by relay R to teletypewriter TTY will be produced at the beginning of each signal received by teletypewriter MTY and this will occur no matter what may be the character of the signal received by teletypewriter MTY. Thus signals will be registered by teletypewriter TTY in conformity with the signals reaching teletypewriter MTY.

Observing the registration of these signals on the machine TTY, the operator may press his letters key and lock it so as to cause the transmitting contacts TC to transmit letters signals continuously. The receiving winding RW will then receive two signals, one obtained from relay R due to the periodic opening and closing of the universal contacts Ki-Kz and another from the transmitting contacts TC. These signals will be combined by the receiving winding RW and they will produce a third signal which may or may not be the letters signal, as will now be explained. The third signal will now be registered by the teletypewriter TTY.

If the curve a of Fig. 3 illustrates the types of pulses received by the receiving winding RW from relay R and curve b represents the types of pulses received by the winding RW from the transmitting contacts TC, the combined signal is shown by curve c. All three curves a, b and c correspond to the letters signal. In other words, if curves a and b are identical and correspond to the letters signal, the third signal of curve c will represent the same signal and hence the machine TTY will register this signal. These conditi-ons will occur when the distant machine TD is operating at the same speed as machine TTY and the two machines are in phase with each other. In this case the teletypewriter TYR will accurately reproduce the signals received from the distant transmitter TD. Under these conditions of equal speed and equal phase, the machine TTY will repeat the letters signal with each received signal. However, the machines TD and TTY may operate at different speeds or in different phases and it is these variables that the apparatus of the invention is intended to detect.

If the curve d represents the signal received by the winding RW from relay R and curve e-the same as curve b--represents the letters signal received by winding RW from the transmitting contacts TC, the curve f will exhibit the resultant signal arising from the combination of the component signals. This signal corresponds to the letter V and the teletypewriter TTY will record this letter. Curves d, e and show that the machines TD and TTY are operating at the same speed, but out of phase with each other. The two machines are out of phase by the time interval of one pulse of the teletypewriter signal. Because the machines are operating at the same speed, the signal V will be recorded by machine TTY in a continuous string. If the machines TD and TTY are out of phase by two pulses but are operating at the same speed, the signal printed by teletypewriter TIY will be the letter X, as shown by a comparison of curves g, h and i. The

letter X will berepeated indenitely. If the phase'differenceis three pulses, the character figures will be repeated indenitely. If `the phase differences are four pulses or five pulses, the characters Q or K, respectively, will be repeated indenitely. Hence an inspection of the record produced by teletypewriter TTY will indicate whether the machine TD is operating at the samespeed'as the teletypewriter TTY and in a constant phase diiierence.

To illustrate the conditions when a more abrupt change in speed is encountered, reference is made to curves k, l, and m` of Fig..3. Here the nrst signal receivedfrom the distanttransmitter TD is out ci' phase with the rst signal fromthe transmitting contacts TC byone pulse, the second signal is out of phase by.two"pulses,.etc. The teletypewriter TTY Will record the signals V, X", gures, Q, K and letters in succession and this cycle of signals will be repeated again and again. The appearance of this cycle of signals is symptomatic of a difference in speed of the two machines. If the speed of the transmitter TD exceeds the speed of' teletypewriter TTY, the order of the signals will be as already noted. However, if the speed of transmitter TD is less than that of teletypewriter TTY, the signalsY will appear on teletypewriter TTY in reversed order during the rst cycle. The frem quency at which the cycle of signals V, X, etc., appears on teletypewriter TTY is proportional to the diiierence in speed of transmitter TD with respect to te-letypewriter TTY. If the transmitter TD is only slightly faster thanteleu typewriter TTY, the signal V may appear 25 times in succession, followed by signal X 25 times in succession, then followed by iigures 25 times insuccession, etc. A wider speed 'discrepancy will beaccompanied by a smaller number of repetitions of each of the'signals of the 6signal cycle, although the number of cycles appearing in any time interval will be correspondingly increased, as already mentioned.

The difference in speed :c between transmitter TD and thetransmitting contacts TC of teletype- Writer TTY may be determined from the following formula:

In this formula A represents the time interval in milliseconds of one of the signal pulses, `A being 22 in a teletypewriter machineoperating on the socalled 60 speed basis; B represents the time in milliseconds for transmitting all of the pulses of any signal or operation including the start pulse and the stop pulse of the signal, B being 163 for signals of the start-stop code; C represents the number of signals or operations per minute for 60 speed transmission and this factor is 368 in the ideal case; and D represents the number of times each signal such as V or X, etc., appears on teletypewriter TTY in any cycle when the transmitter TD is not synchronized with the teletypewriter TTY. The speed of the distant transmitter will be 368mm operations or signals per minute, the positive quantity corresponding to a transmitter TD operating at higher speed than teletypewriter TTY and the negative quantity corresponding to a slower speed.

The following table will give the approximate speed differences o: in the operations or signals per minute corresponding to the number of times each character such as V, X, etc., is repeated 1n a cycle, this number being D in the formula:

None

The apparatus of this invention shown in Fig. l may have automatic counting apparatus associatedtherewith to count .the number of signals such .as V", X, etc., appearing in a single cycle. Such apparatus is shownlin Fig. 2 and may be inserted between terminals W and Y of Fig. 1 so as to be in series with teletypewriter TTY. This apparatus includes a nontyping selector NTS which hasta Contact for each different signal of .the cycle. .For example, contact K11 will be closed when the signal letters is received and the counter CTi will indicate the number of times thatthis signal is. receivedin any cycle. Contact K12 will be closedwhen the signal V is received and counter GT2 will indicate the number of times that this signal is repeated in any cycle. These counters CT1,CT2, CTs, etc., will ordinarily produce the same records at the end of the cycle, whereupon the counters may then be returned to their. initial positions.

The apparatus of this invention may be arranged in different forms as will be apparent from a reading of the specification. The teletypewriter TTY may be replaced by two machines, one a transmitter-distributor arranged to send the signal letters continuously, and the other a receiving only teletypewriter to performthe functions of the (receiving winding RW. These and other modifications are to be assumed as within the scope of this invention.

While this invention has been shownand de scribed in certain particular embodiments merely for illustrative purposes, it will be clearly understood thatrthe general principles of this inventionmay be applied to other and widely varied organizations `without departing from the spirit of theinvention and the scope of the appended claims.

What is claimed is:

.1.. In ateletypewriter system, the combination of an automatic teletypewriter producing a vari ety oi start-stop teletypewriter signals continuously, a relay,.means responsive to said teletypewriter. signals to operate said relay once for each signal, a teletypewriter producing a predetermined signal continuously at a constant speed independent of the speed of said first teletypewriter, and means including the armature and a contact of said relay for immediately modifying the predetermined signals in accordance with the operation of said relay to produce other teletypewriter signals.

2. In a teletypewriter system, the combination of a iirst teletypewriter operating automatically to produce a variety of teletypewriter signals continuously, a second teletypewriter producing a predetermined teletypewriter signal continuously, said second teletypewriter being independent of said iirst teletypewriter and producing said predetermined teletypewriter signal independently of the operation of said first teletypewriter, and means to indicate whether the signals of both teletypewriters are in synchronism, said means operating to produce a sequence of teletypewriter characters consisting 'of a cycle of repetitive series of characters when said teletypewriters are slightly out of synchronism.

3. In a teletypewriter system, the combination of a rst teletypewriter operating automatically to produce a variety of teletypewriter signals continuously, a relay having a contact and an armature adapted to engage said contact when said relay is operated, means responsive to the signals of said first teletypewriter for operating and restoring said relay once for each signal of said first teletypewriter, a source for producing a predetermined teletypewriter signal continuously, and a combining circuit for receiving said predetermined teletypewriter signals interrupted by the contact of said relay to produce other teletypewriter signals to denote the difference in speed between said iirst teletypewriter and said source.

4. In a teletypewriter system, the combination of a teletypewriter producing a predetermined teletypewriter signal continuously, a receiving apparatus adapted to respond to a Variety of start-stopA teletypewriter signals continuously transmitted from a distant station, said receiving apparatus controlling a pair of contacts to open said contacts once for each signal to which said receiving apparatus responds, a circuit for receiving said predetermined signals, said circuit including said contacts for causing its interruption at regular intervals for modifying said predetermined signals.

5. In a teletypewriter system, the combination of a constant speed teletypewriter producing a predetermined teletypewriter signal continuously, a receiving apparatus adapted to respond to a variety of start-stop teletypewriter signals continuously transmitted from a distant station, and means for indicating the relative speed of said receiving apparatus, said means including means for producing pulses the frequency of which corresponds to the frequency at which signals are received by said receiving apparatus and means for combining said pulses and said predetermined signals to produce other teletypewriter signals.

6. In a teletypewriter system, the combination of a remote automatic teletypewriter producing a variety of teletypewriter signals continuously, and means for indicating the relative speed of said remote teletypewriter, said means including receiving apparatus having means associated therewith for producing pulses the frequency-of which is identical with the frequency at which said remote teletypewriter is producing signals, a constant speed teletypewriter producing a predetermined teletypewriter signal continuously,

and means for interrupting said predetermined teletypewriter signals in accordance with said pulses to produce other teletypewriter signals.

7. Apparatus for comparing the speed of an automatic teletypewriter producing a variety of teletypewriter signals continuously with the speed of a constant speed teletypewriter producing a predetermined teletypewriter signal continuously, comprising means for producing a repetitive series of pulses continuously and in synchronism with the reception at said means of the teletypewriter signals of said automatic teletypewriter irrespective of the variety of said signals, means for combining said pulses and said predetermined teletypewriter signals to produce still other teletypewriter signals, and means for recording said other teletypewriter signals.

8. The method of measuring the relative speed of an automatic teletypewriter producing a variety of teletypewriter signals continuously, which consists in producing a predetermined teletypewriter signal repeatedly and at a constant speed, interrupting said predetermined teletypewriter signals once in accordance with each teletypewriter signal of said automatic teletypewriter, converting said interrupted signals into teletypewriter characters, and recording the frequency with which identical characters are consecutively repeated in the sequence of said last-mentioned teletypewriter characters.

9. The method of measuring the relative speed of an automatic teletypewriter producing a variey of teletypewriter signals continuously, which consists in producing teletypewriter signals of the same predetermined character at a predetermined rate, producing pulses in synchronism with the teletypewriter signals of said automatic teletypewriter, modulating said teletypewrlter signals of the same character in accordance with said pulses, and converting the modulated signals into teletypewriter characters, and recording the length of series of consecutively repeated characters among said last-mentioned teletypewriter characters.

WADE B. MARTIN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,298,956 Mason Oct. 13, 1942 1,312,572 Parker Aug. 12, 1919 1,609,383 Shank Dec. 7, 1926 1,800,056 Dirkes Apr. 7, 1931 1,862,474 Fluharty June 7, 1932 

